1. Field of Invention
The present invention relates to tin/lithium oxide composite thin films and methods for manufacturing the same. More particularly, the present invention relates to electrochemical methods for manufacturing tin/lithium oxide composite thin films.
2. Description of Related Art
Lithium ion secondary battery has been widely used in consumer electronics and high power electronics due to its light weight, high electromotive force, and high energy density. Lithium ion secondary battery is classified into high power lithium battery, high capacity lithium battery, and thin film lithium battery. The thin film lithium battery is thin, flexible, and printable and thus is used as a flexible driving power source for IC card, flexible electronic devices and medical electronics.
Metallic lithium was initially used as the cathode material of the lithium ion secondary battery; however, branched structures would form on the surface of the metallic lithium after a number of charge-discharge cycles and thereby would imperil the life cycle and safety of the battery. Lithium cells commonly used in consumer applications have used graphite as the cathode material; however, the graphite cathode has an unsatisfactory low theoretical capacity of about 372 mAh/g. Hence, materials suitable for use as a cathode material have been investigated so as to provide batteries with better capacity and life cycle.
More recently, tin-containing materials have been proposed to be cathode material of the lithium ion secondary battery. If tin dioxide was used as the cathode material, tin dioxide would irreversibly form lithium oxide during the first charge-discharge cycle and thus result in a large irreversible capacity. If tin metal was used as the cathode material, tin would reversibly alloy with lithium and hence would not cause the irreversible capacity loss. However, in the latter case, the relative large of volumetric change would imperil the life cycle of the battery. Therefore, cathodes containing tin or tin oxide are limited to academic research and not applied in commercial products.
In view of the foregoing, there is a need in the related field to provide a cathode material of lithium secondary battery, which has desirable charge-discharge life cycles, and a simplified and cost-effective method for manufacturing the same.